This invention relates to assembly systems and more specifically to a system for assembling fins to the bodies of model rockets.
In the construction of a model rocket several fins, usually three or four, are secured to the exterior of a tubular body of the rocket, usually by gluing, It is very important that these fins be precisely located and aligned on the body. The central plane of each fin should intersect the centerline of the rocket body and the fins should be equiangularly spaced. While the fins may be attached by hand, perhaps using some guide device to assure their alignment at the time they are first placed on the body, such systems tend to be slow, inaccurate and require a relatively high level of skill.
U.S. Pat. No. 3,805,355 to Gornick describes a jig that avoids many of these problems. It has a set of brackets mounted on a base. The brackets each support one fin. A clip holds the fin in position against the bracket. The rocket body is manually centered on the base and the brackets are moved into contact with the body. When the body is centered and all of the brackets are in contact with the body, thumb screws are tightened to secure the radial position of the brackets. The brackets thus cooperate to center and to support the body. The edges of the brackets adjacent the body are angled to avoid gluing the brackets to the body.
This arrangement has proven to have numerous problems. First, it frequently is not a simple task to center the rocket body precisely while at the same time moving and tightening the fin brackets. Another related problem is that the pressure of one or several fin brackets against the usually thin-walled rocket body can distort its shape. When the assembled rocket is moved from the jig, the rocket body returns to its usual cylindrical shape, but the attached fins are no longer properly aligned. Also, because the bracket contacts the rocket body it is difficult to observe the condition of the fin-to-body joint or to correct a poor joint (gaps in the adhesive or an excess of adhesive) until after the adhesive has set and the assembled rocket is removed from the jig.
Other disadvantages of the Gornick arrangement are that it properly aligns only fins having one thickness, it accepts (in its commercially available form) only a limited range of body sizes, namely 0.736 inch to 2.217 inches, and the positioning of the brackets is controlled by the requirement of supporting the body which may not be the best position for supporting and aligning the fins.
It is therefore a principal object of this invention to provide a system for assembling fins on a model rocket that automatically centers the rocket, supports it without deformation of the body and accurately aligns and supports the fins during assembly.
Another object of this invention is to provide an assembly system that requires a low level of skill yet provides a high degree of accuracy in the alignment of the assembled fins.
Still another object is to provide a system that accepts a wide range of rocket body sizes, rocket engine sizes, and fin sizes and shapes.
Yet another object is to provide an assembly that does not interfere with an observation of the fin-to-body adhesive joint or corrections to the joint before the adhesive has set.
A futher object is to provide an assembly system that accommodates both standard thicknesses of fin materials.
A still further object of this invention is to provide an assembly system with all of the foregoing advantages that has fewer component parts than comparable prior art systems and is less costly to manufacture.